Backside illumination image sensors

ABSTRACT

Implementations of image sensor devices may include a through-silicon-via (TSV) formed in a backside of an image sensor device and extending through a material of a die to a metal landing pad. The metal landing pad may be within a contact layer. The devices may include a TSV edge seal ring surrounding a portion of the TSV in the contact layer and extending from a first surface of the contact layer into the contact layer to a depth coextensive with a depth of the TSV.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of the earlier U.S.Utility patent application Ser. No. 16/014,359, entitled “BacksideIllumination Image Sensors,” listing as first inventor Jeffrey Gambino,filed Jun. 21, 2018, now pending, the disclosure of which is herebyincorporated entirely herein by reference.

BACKGROUND 1. Technical Field

Aspects of this document relate generally to image sensors, such asbackside illumination image sensors. More specific implementationsinvolve backside illumination sensors having a through-silicon-via.

2. Background

Image sensors convey information related to an image by communicatingsignals in response to incident electromagnetic radiation. Image sensorsare used in a variety of devices including smart phones, digitalcameras, night vision devices, medical imagers, and many others.Backside illumination image sensors may be used to improve the lightreceiving efficiency of the image sensor, particularly for specificlight wavelengths.

SUMMARY

Implementations of image sensor devices may include athrough-silicon-via (TSV) formed in a backside of an image sensor deviceand extending through a material of a die to a metal landing pad. Themetal landing pad may be within a contact layer. The devices may includea TSV edge seal ring surrounding a portion of the TSV in the contactlayer and extending from a first surface of the contact layer into thecontact layer to a depth coextensive with a depth of the TSV.

Implementations of image sensor devices may include one, all, or any ofthe following:

The TSV edge seal ring may include tungsten.

The TSV edge seal ring may be physically isolated from the metal landingpad.

The device may include a pinning layer directly coupled to one or moresidewalls of the TSV.

The device may include an anti-reflective layer coupled to one or moresidewalls of the TSV.

Implementations of image sensor devices may include athrough-silicon-via (TSV) formed in a backside of an image sensor deviceand extending through a material of a die to a metal landing pad. Themetal landing pad may be within a contact layer. The devices may includea TSV edge seal ring surrounding a portion of the TSV in the contactlayer and extending from a first surface of the contact layer to themetal landing pad.

The TSV edge seal ring may be directly coupled to a diffusion barrierlayer.

The TSV edge seal ring may be directly coupled to one or moreshallow-trench-isolation (STI) regions.

Implementations of image sensor devices may include a firstthrough-silicon-via (TSV) formed in an image sensor device extendingfrom the backside of the image sensor device into a material of a die toa contact layer, a second TSV formed within the first TSV and extendinginto the material of the die to a metal landing pad, wherein the metallanding pad is within a contact layer, and a TSV edge seal ring withinthe contact layer surrounding the second TSV in the contact layer andextending from a first surface of the contact layer into the contactlayer to a depth coextensive with a depth of the second TSV.

The TSV edge seal ring may include tungsten.

The TSV edge seal ring may be directly coupled to the metal landing pad.

The TSV edge seal ring may be physically isolated from the metal landingpad.

The device may include a pinning layer directly coupled to one or moresidewalls of the first TSV.

The device may include an anti-reflective layer coupled to one or moresidewalls of the first TSV.

A perimeter of the TSV edge seal ring may be aligned with a perimeter ofthe first TSV.

A perimeter of the TSV edge seal ring may be larger than a perimeter ofthe first TSV.

A perimeter of the TSV edge seal ring may be smaller than a perimeter ofthe first TSV.

The TSV edge seal ring may be directly coupled to a diffusion barrierlayer.

The TSV edge seal ring may be directly coupled to one or moreshallow-trench-isolation (STI) regions.

The foregoing and other aspects, features, and advantages will beapparent to those artisans of ordinary skill in the art from theDESCRIPTION and DRAWINGS, and from the CLAIMS.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations will hereinafter be described in conjunction with theappended drawings, where like designations denote like elements, and:

FIG. 1 is a cross-section side view of an image sensor device;

FIG. 2 is a cross-section side view of another implementation of animage sensor device;

FIG. 3 is a top view of a portion of a first implementations of an imagesensor device illustrating the relationship between a firstthrough-silicon-via (TSV), a second TSV, and a TSV edge seal ring;

FIG. 4 is a top view of a portion of a second implementation of an imagesensor device illustrating the relationship between a firstthrough-silicon-via (TSV), a second TSV, and a TSV edge seal ring; and

FIG. 5 is a top view of a portion of a third implementation of an imagesensor device illustrating the relationship between a firstthrough-silicon-via (TSV), a second TSV, and a TSV edge seal ring.

DESCRIPTION

This disclosure, its aspects and implementations, are not limited to thespecific components, assembly procedures or method elements disclosedherein. Many additional components, assembly procedures and/or methodelements known in the art consistent with the intended image sensordevices will become apparent for use with particular implementationsfrom this disclosure. Accordingly, for example, although particularimplementations are disclosed, such implementations and implementingcomponents may comprise any shape, size, style, type, model, version,measurement, concentration, material, quantity, method element, step,and/or the like as is known in the art for such image sensor devices,and implementing components and methods, consistent with the intendedoperation and methods.

Referring to FIG. 1 , a cross section side view of an image sensordevice is illustrated. The image sensor device 2 includes a backside 4and a front side 6. The image sensor device 2 may be configured toreceive light from the backside of the device, as indicated by thearrows 100. The image sensor device includes a semiconductor die 8. Invarious implementations, the semiconductor die 8 includes a siliconlayer 10. In other implementations, the semiconductor die 8 may includea layer having silicon dioxide, glass, silicon-on-insulator, galliumarsenide, sapphire, ruby, silicon carbide, polycrystalline or amorphousforms of any of the foregoing, and any other type of layer forconstructing image sensor or semiconductor devices. In implementationsincluding a silicon layer 10, the silicon layer may include a photodiodearray 20 therein.

The image sensor device 2 includes a contact layer 12 having a firstsurface 58 and a second surface 60. In various implementations, thecontact layer may be considered part of the semiconductor die 8, or itmay be considered separate from but coupled to the semiconductor die 8.As used herein, the contact layer 12 is considered part of thesemiconductor die 8 and is not considered separate from the material ofthe semiconductor die 8. In various implementations, the contact layer12 may be an interlayer dielectric (ILD) material 18. The contact layer12 may also include one or more metal layers 14 therein. The metallayers 14 may include one or more metal landing pads 16. In variousimplementations, the metal layers 14 and/or metal landing pads 16 mayinclude aluminum, copper, tungsten, any other metal, and any combinationthereof. In various implementations, the contact layer 12 may includeone or more diffusion barrier layers 34. In particular implementations,the one or more diffusion barrier layers may be adjacent to thebackside/first surface 58, and/or the front side/second surface 60. Thediffusion barrier layer 34 may include SiN or any other material used ina diffusion barrier layer. The contact layer 12 may include otherelements 22 therein, such as gates or other semiconductor elements. Invarious implementations, and as illustrated, the front side 26 of thecontact layer 12 may be coupled to a second semiconductor die 28. Thesecond semiconductor die 28 may include multiple layers therein,including layers 30 and 32. The second semiconductor die 28 may be thesame as or similar to any type of semiconductor die disclosed herein orunderstood by one skilled in the art.

Still referring to FIG. 1 , the semiconductor die 8 includes a firstthrough-silicon-via (TSV) 32 extending from the backside 4 of the imagesensor device 2 and into the silicon layer 10. In particularimplementations, and as illustrated, the first TSV 32 may extend throughthe silicon layer 10 and to the contact layer 12. In variousimplementations, the first TSV 32 may also extend into the contact layer12, and in certain implementations, may extend all the way to a metallanding pad. In various implementations, a pinning layer 38 may becoupled to the sidewalls 36 of the first TSV, a first surface 40 (orbackside) of the semiconductor die 8, and/or to a portion of the base 42of the first TSV 32. The pinning layer 38 may include, by non-limitingexample, HfO₂, Ta₂O₅, or a combination thereof. The pinning layer mayinhibit transfer of pinned voltage therethrough. In particularimplementations, the pinning layer may be directly coupled to thesidewalls 36 of the first TSV, the first surface 40 of the semiconductordie 8, and/or to a portion of the base 42 of the first TSV 32.

In various implementations, an antireflective (AR) layer 44 may becoupled to the sidewalls 36 of the first TSV, a first surface 40 of thesemiconductor die 8, and/or to a portion of the base 42 of the first TSV32. The AR layer 44 may include, by non-limiting example, SiO₂ or anyother material that acts to prevent reflection of light. In particularimplementations, and as illustrated by FIG. 1 , the AR layer 44 may bedirectly coupled over the pinning layer 38. In other implementations,the image sensor device may not include a pinning layer 38 and the ARlayer 44 may be directly coupled to the sidewalls 36 of the first TSV,the first surface 40 of the semiconductor die 8, and/or to a portion ofthe base 42 of the first TSV 32. In implementations where the first TSVextends all the way to the metal landing pad, the image sensor devicemay not include more TSVs than the first TSV. In such implementations, adiffusion barrier layer may be coupled within the TSV and may bedirectly coupled to the metal landing pad.

In various implementations, and as illustrated by FIG. 1 , the imagesensor device 2 may include a second TSV 46. The second TSV 46 may beformed within the first TSV 32 (within the perimeter of the first TSV32) and extends into the semiconductor die 8 material. As illustrated,the width of the second TSV 46 is less than the width of the first TSV32. In various implementations, the second TSV 46 may extend partiallythrough the silicon layer 10 if the first TSV 32 did not extendcompletely through the silicon layer. The second TSV 46 may also extendinto the contact layer 12. In particular implementations, the second TSV46 extends to the metal landing pad 16 within the contact layer 12. Invarious implementations, a metal layer 48 may be applied within thesecond TSV 46. The metal layer 48 may be any type of metallic diffusionbarrier layer, including, by non-limiting example, Ti, TiN, Al, W, Cu,Ta, TaN, and any combination thereof. In such implementations, the metallayer 48 may be indirectly or directly coupled to the sidewalls of thesecond TSV 46 and/or the base 50 of the second TSV. The metal layer 48may also serve as a mobile ion barrier, moisture barrier, hydrogenbarrier, and as a barrier against any other contaminant entering thesecond TSV 46 or the material of the die itself. The metal layer 48 mayalso be coupled to a portion of the base 42 of the first TSV 32 and inimplementations having a pinning layer 38 and/or AR layer 44, the metallayer may be coupled over the pinning layer and/or AR layer within thefirst TSV. The metal layer 48 may extend along a portion of the backside4 of the image sensor device 2. In various implementations, a sealantmay be used in place of the metal layer 48.

Still referring to FIG. 1 , the image sensor device 2 may include one ormore shallow trench isolation (STI) regions 52 within the semiconductordie 8. In various implementations, the STI regions 52 may be formedwithin the silicon layer 10. The STI regions 52 may be adjacent to orcontact the sidewalls 36 of the first TSV 32. In particularimplementations, the STI regions 52 may be formed adjacent to a cornerformed between the sidewalls 36 of the first TSV 32 and the base 42 ofthe first TSV. In other implementations, the STI regions 52 may beformed below the first TSV 32. In other implementations, rather than STIregions, the semiconductor die 8 may include regions doped counter tothe doping of the silicon layer 10. As an example, if the silicon layer10 was P doped, the regions in place of the STI regions may be n or n+doped.

The image sensor device 2 includes a TSV edge seal ring 62. The TSV edgeseal ring 62 may be, by non-limiting example, tungsten, copper, silver,gold, any other metal, any other metal alloy, or any combinationthereof. In particular implementations, the TSV edge seal ring 62 may beformed of tungsten. As illustrated, the TSV edge seal ring 62 is withinthe contact layer 12. In such implementations, the TSV edge seal ring 62may surround the second TSV 46 in the contact layer 12. In otherimplementations, the TSV edge seal ring 62 may be partially within thesilicon layer 10. In various implementations, the TSV edge seal ring mayextend from a first surface 58 of the contact layer 12 into the contactlayer to a depth coextensive with a depth of the second TSV 46. Insimilar implementations, the TSV edge seal ring 62 may extend from thebase 42 of the first TSV, or a location coextensive with a depth of thebase of the first TSV, to a depth coextensive with a depth of the secondTSV 46. In particular implementations, the TSV edge seal ring may bedirectly coupled to the metal landing pad 16. The TSV edge seal ring mayalso be directly coupled to a diffusion barrier layer 34 and/or one ormore STI regions 52. As illustrated by FIG. 1 , and as later describedin relation to FIG. 3 , the perimeter of the TSV edge seal ring 62 maybe larger than the perimeter of the first TSV. In such implementations,the STI regions 52 and/or the diffusion barrier layer 34 may cover thegap between the edge of the first TSV 32 and the TSV edge seal ring 62in order to prevent ingress of any contaminants to the area immediatelysurrounding the interface between the second TSV 46 and the metallanding pad 16.

Referring to FIG. 3 , a top view of a portion of a first implementationof an image sensor device illustrating the relationship between a firstTSV, a second TSV, and a TSV edge seal ring is illustrated. The top viewof FIG. 3 corresponds to FIG. 1 in that the TSV edge seal ring 64 hasthe largest perimeter, the first TSV 66 has a perimeter just smaller andwithin the perimeter of the TSV edge seal ring 64, and the second TSV 68has the smallest perimeter and is located in the center of the first TSV64. In various implementations, the distance between the perimeters ofthe TSV edge seal ring 64, the first TSV 66, and the second TSV 68 mayvary, however, in particular implementations, and as illustrated, theperimeter of the first TSV 66 is made only slightly smaller than theperimeter of the TSV edge seal ring 64 in order to allow space for asmall barrier (STI region or diffusion barrier layer) between theperimeter of the TSV edge seal ring and the perimeter of the first TSV.Referring to FIG. 4 , a top view of a portion of a second implementationof an image sensor device illustrating the relationship between a firstTSV 72, a second TSV 74, and a TSV edge seal ring 70 is illustrated.

Contrary to FIG. 3 , in various implementations, the perimeter of thefirst TSV 72 may be larger than the perimeter of the TSV edge seal ring70, and the perimeter of the TSV edge seal ring 70 may be larger thanthe perimeter of the second TSV 72. In the implementation illustrated byFIG. 4 , the TSV edge seal ring 70 is formed below the first TSV 72. Asillustrated by FIG. 4 , the TSV edge seal ring 70 is located closer tothe perimeter of the first TSV 72 and further from the perimeter of thesecond TSV 74, however, in other implementations the TSV edge seal ringmay be located anywhere between the perimeter of the first TSV 72 andthe perimeter of the second TSV 74. Referring to FIG. 5 , a top view ofa portion of a third implementation of an image sensor deviceillustrating the relationship between a first TSV 76, a second TSV 80,and a TSV edge seal ring 78 is illustrated. In various implementations,the perimeter of the first TSV 76 may be the same size and shape as theperimeter of the TSV edge seal ring 78. In such implementations, theperimeter of the first TSV 76 may line up with the perimeter of the TSVedge seal ring 78. Similar to the implementation illustrated by FIG. 4 ,the TSV edge seal ring 78 may be formed under the edge of the first TSV76. The perimeter of the second TSV 80 may be smaller than the perimeterof the first TSV 76 and the TSV edge seal ring 78.

In implementations having only a single TSV that extends to the metallanding pad, the TSV edge seal ring may surround the portion of the TSVin the contact layer. In such implementations, the perimeter of the TSVedge seal ring is greater than the perimeter of the first TSV. An STIregion and/or diffusion barrier layer may cover the gap, if a gapexists, between the TSV and the TSV edge seal ring. Thus, in eitherimplementations with a single TSV or implementations with a first andsecond TSV, the TSV edge seal ring 62 provides a barrier for theinterface between the TSV coupled to the metal landing pad and the metallanding pad 16. Specifically, the TSV edge seal ring 62 may serve as abarrier to, by non-limiting example, moisture, mobile ions, andhydrogen.

Referring to FIG. 2 , a cross-section side view of anotherimplementation of an image sensor device is illustrated. The imagesensor device 82 is similar to the image sensor device 2 of FIG. 1 . Theprimary difference is that the TSV edge seal ring 84 is physicallyisolated from the material of the metal landing pad 86. As illustratedin FIG. 2 , the TSV edge seal ring 84 is directly coupled to one or moremetal pads 88. One or more gaps 90 physically isolate the one or moremetal pads 88, and in turn, the TSV edge seal ring 84, from the metallanding pad 86. In such implementations, in order to inhibit the ingressof moisture, hydrogen, ions, or other contaminants into the area 92immediately surrounding the interface 96 between the second TSV 94 andthe metal landing pad 86, the image sensor device may include anadditional diffusion barrier layer 98. The diffusion barrier layer 98may be any type of diffusion barrier layer disclosed herein. Thediffusion barrier layer 98 may be directly coupled to the metal landingpad 86 and one or more metal pads 88. The diffusion barrier layer 98 mayalso be a barrier to prevent ingress of contaminants through the one ormore gaps 90.

In various implementations, a method of forming the image sensor deviceof FIG. 1 or FIG. 2 may include forming the desired metal layers, metallanding pads, diffusion barrier layers, TSV edge seal ring, and anyother elements in the contact layer (which may be an ILD). In variousimplementations, the TSV edge seal ring may be directly coupled to, andmay even be the same material, as the metal landing pad. In particularimplementations, the TSV edge seal ring may be formed as a singlecontinuous piece with the metal landing pad. In other implementations,the TSV edge seal ring may be physically isolated from the metal landingpad, similar to the implementation illustrated in FIG. 2 . The methodmay include coupling a wafer to the contact layer. The wafer may includea silicon layer (or any other die/wafer material previously disclosedherein) having a photodiode array to the contact layer. The wafer mayalso include a plurality of STI or counter doped regions. In variousimplementations, the method includes thinning the wafer from thebackside of the wafer to a desired thickness. The wafer then may bepatterned and a TSV may be formed in the wafer. In implementationshaving STI or counter doped regions, the edge of the TSV may beconfigured to border such regions. The TSV is formed from the backsideof the device. The width and length of the TSV may be configured toallow the perimeter of the TSV to be smaller and fit within a perimeterof the TSV edge seal ring, to be larger and surround a perimeter of theTSV edge seal ring, or to line up with a perimeter of the TSV edge sealring. The TSV may be formed through the silicon layer (or other wafermaterial). In various implementations (such as implementations havingtwo TSVs), the TSV does not extend into the contact layer, however, inother implementations the TSV does extend into the contact layer and mayeven extend to a metal landing pad within the contact layer. The methodmay include depositing a pinning layer over the backside of the waferand within the TSV. The pinning layer may coat the sidewalls and thebase of the TSV. Similarly, the method may include depositing an ARlayer over the backside of the wafer and within the TSV. The AR layermay be deposited over the pinning layer in implementations having apinning layer.

In implementations where the TSV does not extend to the metal landingpad, the method may include patterning the base of the existing TSV andforming a second TSV therein. The second TSV in various implementationsmay have a smaller width than the existing first TSV and may extend intothe contact layer (and through the pinning layer and AR layer if theyexist) and to the metal landing pad. In various implementations, themethod may include forming a diffusion barrier layer within the secondTSV. The diffusion barrier layer may also coat the inside of the firstTSV and may extend over onto a backside of the wafer in addition tocoating the base and sidewalls of the second TSV.

In various implementations, a backside metal may be coupled to thebackside of the image sensor device, such as, by non-limiting example,copper, silver, gold, aluminum, nickel, tungsten, or any other metal,metal alloy, or combination thereof. The method includes singulating thewafer. The singulated image sensor devices (or the wafer beforesingulation) may be hydrogen annealed.

In places where the description above refers to particularimplementations of image sensor devices and implementing components,sub-components, methods and sub-methods, it should be readily apparentthat a number of modifications may be made without departing from thespirit thereof and that these implementations, implementing components,sub-components, methods and sub-methods may be applied to other imagesensor devices.

1. An image sensor device comprising: a through-silicon-via (TSV) formedin a backside of an image sensor device and extending into a die to ametal landing pad within a contact layer; and a TSV edge seal ringsurrounding a portion of the TSV in the contact layer and extending froma first surface of the contact layer into the contact layer to a depthcoextensive with a deepest depth of the TSV.
 2. The image sensor deviceof claim 1, wherein the contact layer is comprised within the die. 3.The image sensor device of claim 1, wherein the TSV edge seal ring isdirectly coupled to the metal landing pad and a perimeter of the TSV isentirely within a perimeter of the metal landing pad.
 4. The imagesensor device of claim 1, wherein the TSV edge seal ring is physicallyisolated from the metal landing pad.
 5. The image sensor device of claim1, further comprising a pinning layer directly coupled to one or moresidewalls of the TSV.
 6. The image sensor device of claim 1, furthercomprising an anti-reflective layer coupled to one or more sidewalls ofthe TSV.
 7. An image sensor device comprising: a through-silicon-via(TSV) formed in a backside of an image sensor device and extending intoa die to a metal landing pad, wherein the metal landing pad is within acontact layer of the die; and a TSV edge seal ring surrounding a portionof the TSV in the contact layer and extending only from a first surfaceof the contact layer to the metal landing pad.
 8. The image sensordevice of claim 7, wherein the TSV edge seal ring is directly coupled toa diffusion barrier layer.
 9. The image sensor device of claim 7,wherein the TSV edge seal ring is directly coupled to one or moreshallow-trench-isolation (STI) regions.
 10. The image sensor device ofclaim 7, wherein a deepest depth of the TSV terminates at the metallanding pad.
 11. The image sensor device of claim 7, wherein a perimeterof the TSV is entirely within a perimeter of the metal landing pad. 12.An image sensor device comprising: a first through-silicon-via (TSV)formed in an image sensor device extending from the backside of theimage sensor device into a material of a die to a first surface of acontact layer; a second TSV formed within the first TSV and extendinginto the material of the contact layer to a metal landing pad; and a TSVedge seal ring within the contact layer surrounding the second TSV inthe contact layer and extending from the first surface of the contactlayer into the contact layer.
 13. The image sensor device of claim 12,wherein the TSV edge seal ring is directly coupled to the metal landingpad.
 14. The image sensor device of claim 12, wherein the TSV edge sealring is physically isolated from the metal landing pad.
 15. The imagesensor device of claim 12, further comprising an anti-reflective layercoupled to one or more sidewalls of the first TSV.
 16. The image sensordevice of claim 12, wherein a perimeter of the TSV edge seal ring isaligned with a perimeter of the first TSV.
 17. The image sensor deviceof claim 12, wherein a perimeter of the TSV edge seal ring is largerthan a perimeter of the first TSV.
 18. The image sensor device of claim12, wherein a perimeter of the TSV edge seal ring is smaller than aperimeter of the first TSV.
 19. The image sensor device of claim 12,wherein the TSV edge seal ring is directly coupled to a diffusionbarrier layer.
 20. The image sensor device of claim 12, wherein the TSVedge seal ring is directly coupled to one or moreshallow-trench-isolation (STI) regions.